Unified stream and batch processing with Apache Flink’s relational APIs

Apache Flink's DataStream API is very expressive and gives users precise control over time and state. However, many applications do not require this level of expressiveness and can be implemented more concisely and easily with a domain-specific API. SQL is undoubtedly the most widely used language for data processing but usually applied in the domain of batch processing. Apache Flink features two relational APIs for unified stream and batch processing, the Table API, a language-integrated relational query API for Scala and Java, and SQL. A Table API or SQL query computes the same result regardless whether it is evaluated on a static file or on a Kafka topic. While Flink evaluates queries on batch input like a conventional query engine, queries on streaming input are continuously processed and their results constantly updated and refined. In this talk we present Flink’s unified relational APIs, show how streaming SQL queries are processed, and discuss exciting new use-cases.